40, 50 and 100 GB/S OPTICAL TRANSCEIVERS/TRANSPONDERS IN 300PIN AND CFP MSA MODULES

ABSTRACT

Disclosed by way of exemplary embodiments, a 40/50/10 Gb/s Optical Transceivers/transponders which use opto-electronic components at data rates collectively that are lower than or equal to half the data rate , using two optical duobinary carriers. More specifically, the exemplary embodiments of the disclosed optical transceivers/transponders relate to a 43 Gb/s 300 pin MSA and a 43˜56 Gb/s CFP MSA module, both include a two-carrier optical transceiver and the appropriate hardware architecture and MSA standard interfaces. The two-carrier optical transceiver is composed of a pair of 10 Gb/s optical transmitters, each using band-limited duobinary modulation at 20˜28 Gb/s. The wavelength channel spacing can be as little as 19˜25 GHz. The same principle is applied to a 100 Gb/s CFP module, which is composed of four tunable 10 Gb/s optical transmitters, with the channel spacing between optical carriers up to a few nanometers.

RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationNo. 61/242,807 entitled “40, 50, and 100 Gb/s OpticalTransceivers/Transponders in 300 pin and CFP MSA Modules,” filed on Sep.16, 2009, U.S. Provisional Patent Application No. 61/179,956, entitled“Optical Network Architecture and Apparatus for High Capacity Upgrade”filed on May 20, 2009 and U.S. Provisional Patent Application No.61/186,325, entitled “Part Two of ‘Optical Network Architecture andApparatus for High Capacity Upgrade,’” filed Jun. 11, 2009, each hereinincorporated by reference in their entirety for all purposes.

DESCRIPTION OF THE RELATED ART

The present disclosure relates to optical communications based onoptical wavelength division multiplexing (WDM).

BACKGROUND OF THE INVENTION

Current commercially available 40 Gb/s 300 pin modules such as describedin 300 pin MSA Group, Reference Document for “300 pin 40 GbTransponder,” Public Document Edition 3, Jul. 19, 2002, found on theworld wide web at 300pinmsa.org, use direct detection methods. Thesetransponders are mostly based on four modulation formats: (a) 40 Gb/sNRZ (non-return-to-zero), (b) 40 Gb/s duobinary, (c) 40 Gb/sdifferential phase-shift-keying (DPSK), and (d) 2×20 Gb/s differentialquadrature phase-shift-keying (DQPSK). 40 Gb/s NRZ has a severedispersion-limited transmission distance of around 2-10 km and isusually for short-distance “client-side” applications. 40 Gb/s duobinarymodulation was used in the first-generation long-haul transmissionsystems, but has a severe limitation in terms of both poor chromaticdispersion (CD) and polarization mode dispersion (PMD) tolerance, 40Gb/s DPSK and 2×20 Gb/s DQPSK both exhibit good optical signal-to-noiseratio (OSNR) performance. DPSK has limited CD and PMD tolerance, whileDQPSK improves both CD and PMD tolerance by halving the symbol rate.However, DQPSK requires much more complicated structure than DPSK,duobinary, and NRZ, and therefore has a higher cost. 40 Gb/s DPSK and2×20 Gb/s DQPSK require thermally-tuned phase demodulator. 40 Gb/sduobinary, 40 Gb/s DPSK, and 2×20 Gb/s DQPSK require thermally-tunedoptical dispersion compensator. These thermally-tuned devices are allvery slow, with a tuning time in the range of tens of seconds. As aresult, none of these modulation formats are suitable for a ROADM(reconfigurable optical add-drop multiplexing)-based optical network,which needs to re-configure wavelengths dynamically and a fast trafficrecovery time.

Another modulation technique is 2×20 Gb/s bandlimited-optical duobinary(BL-ODB). 2>20 Gb/s BL-ODB was proposed in J. Yu, et al., “Opticalsubchannels from a single lightwave source,” U.S. Patent Publication No.US2008/0063396 A1, published Mar. 13, 2008, and in L. Xu et al.,“Spectral Efficient Transmission of 40 Gbps per Channel over 50 GHzSpaced DWDM Systems Using Optical Carrier Suppression, Separation andOptical Duobinary Modulation,” paper NTuC2, Optical Fiber CommunicationsConference, 2006. In these systems, both the optical modulator andphoto-detector use complex 40 Gb/s components.

The concept of using structurally simpler and more common 10 Gb/sopto-electronic components for 40 Gb/s duobinary data was apparentlyfirst proposed in H. L. Lee et al., “Duobinary Optical Transmitter”, asdisclosed in related U.S. Pat. No. 7,215,892 B2, issued May 8, 2007 andU.S. Pat. No. 7,224,907 B2, issued May 29, 2007.

From packaging perspective, although it is challenging to fit multipleopto-electronic components into a 40 Gb/s 300 pin MSA module, it is evenmore challenging to fit those opto-electronic components in a muchsmaller space offered by CFP MSA module as specified in CFP Draft 1.0,Mar. 23, 2009.

The C (Latin letter C for 100 or centum) form-factor pluggable (CFP) isfrom a multi-source agreement (MSA) for a standard common form-factorfor high-speed transmission digital signals. The CFP supports 100 Gb/sand 40 Gb/s using 10 and 4 lanes in each direction (Rx and Tx),respectively, with 10 Gb/s in each lane.

SUMMARY OF THE INVENTION

Disclosed herein is a modulation technique and an apparatus embodyingthe same that offers even lower cost than currently commerciallyavailable duobinary and DPSK 300 pin transponders, and yet withcomparable system performance as DQPSK 300 pin transponders. Thismodulation technique, 2×20 Gb/s bandlimited-optical duobinary (DualBL-ODB) modulation, uses only a pair of 10 Gb/s optical modulators inthe optical modulators to achieve 40, 50 Gb/s transmission rates, andtwo pairs of 10 Gb/s optical modulators to achieve 100 Gb/s transmissionrates. It offers the smallest possible form factor for 40, 50, and 100Gb/s transmission rates. The modulation technique also allows fasttraffic recovery in an optical network with dynamic wavelength switchingand routing.

The presently disclosed exemplary transceiver combines the 20-28 Gb/sBL-ODB modulation technique and 10 Gb/s opto-electronic modulationcomponents to achieve the best balance between cost and performance for40/50/100 Gb/s transmission. Further, the presently disclosedtransceivers/transponders can use existing IC chips with appropriatehardware interfaces to accommodate this modulation technique.

By using the recently developed 10 Gb/s tunable Transmitter OpticalSubAssemblies (TOSAs) (which require a much smaller volume thanconventional Integrated Tunable Laser Assemblies (ITLAs)) based onsemiconductor Mach-Zehnder modulators, it is possible to fit allopto-electronic components in a line-side and in some applicationsclient-side CFP transceiver module carrying 40 Gb/s and 100 Gb/scapacity.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1A illustrates exemplary 300 pin 2×(20^(˜)23) Gb/s modulesdescribed herein, and shows that the duobinary encoder(s) can beimplemented within or after the 16:2 multiplexer.

FIG. 1B illustrates the different possibilities of the “Tunable 10G TX”as employed in the various exemplary embodiments.

FIG. 2 illustrates exemplary optimum channel spacing between the twooptical carriers in FIG. 1A when the two carriers are launched withorthogonal polarizations.

FIGS. 3A, 3B, and 3C illustrate exemplary CFP 2×(20˜23) Gb/s modules.

FIGS. 4A and 4B illustrates an exemplary 56 Gb/s (2×28 Gb/s) CFP MSAmodule with two optical sub-carriers spaced between 19 and 25 GHz.

FIG. 5 illustrates an exemplary 100 GbE CFP module using 4×25 Gb/soptical transceivers/transponders, wherein each optical transceiver usesonly 10 Gb/s optical modulators and the optical sub-carriers are spacedbetween 100 and 800 GHz.

DETAILED DESCRIPTION OF THE INVENTION

Various aspects and exemplary embodiments of the present disclosure arenow described with reference to the drawings. In the followingdescription, for purposes of explanation, numerous specific details areset forth in order to provide a thorough understanding of one or moreaspects. It may be evident, however, that such aspect(s) may bepracticed without these specific details.

The term “or” is intended to mean an inclusive “or” rather than anexclusive “or.” That is, unless specified otherwise, or clear from thecontext, the phrase “X employs A or B” is intended to mean any of thenatural inclusive permutations. That is, the phrase “X employs A or B”is satisfied by any of the following instances: X employs A; X employsB; or X employs both

A and B. In addition, the articles “a” and “an” as used in thisapplication and the appended claims should generally be construed tomean “one or more” unless specified otherwise or clear from the contextto be directed to a singular form.

Various aspects or features will be presented in terms of systems thatmay include a number of devices, components, modules, and the like. Itis to be understood and appreciated that the various systems may includeadditional devices, components, modules, etc. and/or may not include allof the devices, components, modules, etc., discussed in connection withthe figures. A combination of these approaches may also be used.

Disclosed herein, for the first time, is how to combine appropriatehardware chips and interfaces (e.g., SFI5.1, 4× XFI, 10× XFI, etc.) withdual-carrier duobinary optical transceivers/transponders, with eachoptical carrier carrying 20-28 Gb/s data stream, to achieve atransceiver/transponder capacity of approximately 40 Gb/s, 50 Gb/s, and100 Gb/s. Each 20-28 Gb/s optical carrier requires only a 10 Gb/soptical modulator in the transceiver, with or without a receiverelectronic equalizer operating at 20-28 Gb/s for duobinary modulation.Consequently, a 40 Gb/s optical transceiver is composed of only twofixed or tunable wavelength 10 Gb/s transmitters (TXs) in thetransceiver, and a 100 Gb/s optical transceiver is composed of only fourfixed or tunable wavelength 10 Gb/s optical TXs.

When the channel spacing between optical carriers is as narrow as 19˜25GHz, the size of the receiver-side 1×2 array-waveguide (AWG), which isused to separate two narrowly spaced optical carriers, may be too costlyor sometimes too big to fit into a CFP module. In that case, the AWGdevice is pushed outside the CFP module and used instead as ade-interleaver located between a transmission link and conventional40-ch or 80-ch DWDM demultiplexers. A optical architecture using a 1×2AWG slicer as the de-interleaver are disclosed in U.S. ProvisionalPatent Application No. 61/179,956, May 20, 2009 and U.S. ProvisionalPatent Application No. 61/186,325, Jun. 11, 2009, both hereinincorporate by reference in their entirety for all purposes.

Exemplary Configurations

FIGS. 1A and 1B show exemplary hardware and optical configurations of a40 Gb/s 300 pin transceiver module. As illustrated, on a host board 100are mounted an external 40 Gb/s FEC chip 110 electrically connected viaa standard SFI5.1 connector to a 300 pin 2×(20˜23) Gb/s module 120.Within the module 120 is a 300 pin connector 122, which connects to theexternal FEC chip 110 via the SFI5.1SFI5.1 interface. The FEC chip 110in turn is connected to a 16:2 multiplexer (MUX) 124, which has aduobinary precoders in this exemplary embodiment, and has sufficientelectronic buffer to manage the skew between the two 20-23 Gb/s lanes.Note that a duobinary precoder sometimes is termed a “differentialencoder”.

If the MUX 124 does not have a doubinary precoder, then an externalprecoder is used immediately after the MUX 124. The MUX 124 separatesthe 40-46 Gb/s signal into two 20-23 Gb/s differentially encoded NRZsignals, each separately amplified in driver amps 126 a and 126 b, thenpassing through low pass filters (LPFs) 125 a, 125 b (which can beseparate filters or different ports of the same LPF). Each LPF serves asa duobinary encoder. Alternatively, the LPF filters 125 a, 125 b cancome first, and the low-pass filtered signals amplified linearly bydriver amps 126 a and 126 b; in the future when extremely low-drivevoltage InP MZIs are commonly commercially used instead of LN MZIs, orthe driver amps are integrated inside the MUX chip 124, these driveramps may not be required.

It should be noted that in the exemplary embodiments disclosed herein,driver amplifiers with a small group delay variation (such that a 20-28Gb/s signal is not distorted) should be used. The low-pass filtered andamplified signals then drive respective tunable 10 Gb/s transmitters 127a, 127 b.

As for the tunable 10 Gb/s transmitters, it should be noted that FIG. 1Ashows two tunable laser assemblies (ITLAs), though one integrated ITLAcould be used to produce both carrier wavelengths if a wavelengthseparator or the like is employed. Further, FIG. 1B shows variousimplementations of the tunable 10G/s transmitters 127 a, 127 b. In afirst variation, an ITLA 128 a can be coupled to a 10 G/s LN MZI 128 b.In a second variation, a mini- or micro-ITLA 128 a can be coupled to a10 G/s InP MZI. In a third variation, an integrated InP chip 128 thathas both a tunable laser and an MZI is employed. Polymer-based opticalmodulators can also be used. In all cases of FIG. 1B, the modulators canbe zero-chirp or pre-chirped.

The modulated optical outputs from the 10 Gb/s MZIs 127 a, 127 b arethen coupled in to an optical fiber via a 2×1 optical coupler orpolarization-maintaining beam combiner (PMBC)129. On the receive side ofthe 300 pin 2×(20˜23) Gb/s module is a 1×2 array waveguide (AWG) slicer130, such as a 1×2 cyclic array waveguide with a cycle of 50 GHz, forexample, that receives the optical signal from a optical fiber or thelike and split into two signals. Each received and separated signal isfeed into a respective 20 Gb/s receiver 131 a, 131 b and then onto anelectronic dispersion compensators (EDC) or equalizers 132 a, 132 b.Note that the 20 Gb/s receiver should be broadly understood to have anamplitude and flat group-delay bandwidth higher than that of a 10 Gb/sreceiver, but whether the bandwidth is 18 GHz or 12 GHz, for instance,depends on the effectiveness of the EDC. Thereafter, the receivedsignals are input into a 2:16 demultiplexer 134, and the demultiplexedsignal is then transmitted (via e.g., a SF15.1SFI5.1 interface and a 300pin connector 122) to the external FEC 110. The error corrected anddecoded signal can then be taken off the host board 100 for use in thelarger communications system.

A key component in this particular exemplary implementation is theelectronic IC MUX/DEMUX 124, 134, which performs the 16:2 and 2:16serdes (serialize and de-serialize) function, with an SFI 5.1 interface.As illustrated, it would have a duobinary precoder built therein. Butdepending on the IC actually used, it may not have a duobinary encoder.If this is the case, the duobinary precoder can be located immediatelyafter the MUX 124.

Note also that the two electronic dispersion compensators (EDCs) 132 a,132 b operating at 20˜23 Gb/s can be either stand-alone chips, or can beintegrated into the 2:16 DEMUX IC 124, 134. The purpose of the EDCs isto further improve the CD and PMD tolerance, and optical filteringtolerance of the 2×20 Gb/s BL-ODB modulation signals. The EDCs can alsobe used to improve the OSNR performance, for example, by purposelynarrowing the bandwidth of the AWG slicer 130 to reduce the noise, andlet the EDC to correct the increased inter-symbol-interference (ISI)caused by the narrower AWG slicer bandwidth. If a system does notrequire these improved CD, PMD, and OSNR performances, the two EDCs donot have to be used.

As can be seen, the optical part of the transceiver module 100illustrated in FIG. 1A is simply a pair of duobinary opticaltransceivers/transponders, with a 1×2 AWG (array waveguide) device usedto separate the two optical carriers spaced between 19˜25 GHz in thisexample. The channel spacing between the two optical carriers depends onwhether a polarization-maintaining beam combiner (PMBC) is used or not.In the case when the two optical carriers are launched with orthogonalpolarization states, an optimum channel spacing can be found in FIG. 2to be around 19-20 GHz, as evident from the optical signal to noiseratio (OSNR) vs. channel spacing (in GHz) graph of FIG. 2. Note that incase there is non-negligible polarization-dependent-loss (PDL) in theoptical transmission system which causes the received optical powerlevel of the two polarizations to be different, a feedback signaling canbe sent from the receiving end to the transmitting end to increase thepower of the lower power wavelength so that the power levels at thereceiver can be equalized.

FIG. 3A illustrates an embodiment in CFP package, which is differentfrom the 300-pin package in FIG. 1. A chip 321 that converts 4× XFI toSFI5.1 interface is added before the original 16:2 MUX and 2:16 DEMUX inFIG. 1. This chip may or may not contain the forward-error-correction(FEC) function.

FIG. 3B illustrates another embodiment in CFP package. In FIG. 3B, theoriginal 16:2 MUX 124 and 2:16 DEMUX 134 in FIG. 1 are replaced withpairs of 2:1 TDM (time domain multiplexing) MUXs 324 a, 324 b, and 1:2TDM DEMUXs 334 a, 334 b. Note too that the electrical input interfacehas been changed from SFI5.1 in FIGS. 1 to 4× XFI in FIG. 3B.

In a CFP package, in order to save space, integrated tunable laserassemblies (ITLAs) and 10G lithium-niobate Mach-Zehnder Interferometer(MZI) 128 in FIG. 1 can be replaced by (a) an integrated single-chip InPlaser MZI (3rd variation of FIG. 1B), or (b) a micro- or mini-ITLA 128 ain combination with a LN or InP MZI 128 b (1st and 2nd variations ofFIG. 1B). In addition, owing to the fact that InP MZI should requiremuch less microwave driving power, the power consumption can be reducedfurther, in the variations shown in FIG. 1B.

In the example of FIG. 3A and 3C, the duobinary precoders areincorporated in an IC chip that provides the MUX 124. In the example ofFIG. 3B, the duobinary precoders are incorporated in the IC chips 324 aand 324 b that provides 2:1 MUX function. Otherwise, the two duobinaryprecoders should be located right after the 2:1 MUX output ports.

In FIG. 3A and 3C, MUX 124 separates the 40-46 Gb/s signal into two20˜23 Gb/s signals, each separately passing through driver amps 126 a,126 ba, then through low pass filters (LPFs) 125 a, 125 b. The order ofthe driver amps and low pass filters can be reversed, and in someembodiments these driver amps may not be required. The low-pass filteredand amplified signals then drive respective tunable 10 Gb/s TX 127 a,127 b. Arrangements such as variations (2) and (3) in FIG. 1B are smallenough to fit into the CFP MSA module 320 in this exemplary embodiment.Variation (1) could be used if the components are made to fit into thisspace. The output carrier waves from the tunable 10G TX 127 a, 127 b aremodulated in accordance with the low-pass filtered and amplified signalby the 10 Gb/s MZIs (need to have numbers in FIG. 1B) in this exemplaryembodiment.

Note that the arrangement in FIG. 1B, variations (2) and (3) impliesthat the InP-based MZI allows duobinary modulation, i.e., the opticalpower-to-bias voltage transfer function is symmetrical with respect tothe zero bias voltage.

In FIG. 3C, The modulated optical outputs the tunable 10G TX 127 a, 127b are then transmitted via a MPO jumper connector 350 to an externalDWDM MUX/DEMUX box 310. The external DWDM MUX/DEMUX box 310 is connectedto a 1×2 25/50 GHz interleaver 314, that receives the optical signalfrom the external DWDM MUX/DEMUX box 310 and combines them into anoptical fiber constituting the transmission link. In this configuration,the two wavelengths generated the tunable 10G TX 127 a, 127 b are called“even” and “odd” channels, respectively. They need to be separated by 25GHz in this exemplary embodiment. Each even wavelength is first combinedwith other >80 even wavelengths via the even multiplexer 313 a, and eachodd wavelength is first combined with other >80 odd wavelengths via theodd multiplexer 313 b. The two groups of even and odd wavelengths arethen combined via the interleaver 314.

On the receive side in FIG. 3C, each received optical signal isseparated into even and odd wavelengths via the 1×2 de-interleaver 315,and the >80 odd wavelengths are input to the DEMUX 316 a and the >80even wavelengths are input to the DEMUX 316 b of the external DWDM box310. An even and an odd wavelengths within the same 50 GHz window areconnected to the CFP module 320 via two fibers. Note that for each CFPmodule 320, there are two input fibers and two output fibers, and toavoid 4 fibers and 8 connectors, a jumper cable containing 4 fibers andtwo MPO connectors can be used instead (although the 4 fiber connectionis still a viable approach). Within the CFP module 320, the respectivesignals are fed to respective 20 Gb/s receivers 131 a, 3131 b, and thenonto an electronic dispersion compensator (EDC) 132 a, 132 b.Thereafter, the received signals are input into a 2:16 demultiplexer329, and the demultiplexed signal is then transmitted (via, e.g., aSF15.1 connector) to the external FEC 321 for output to externalhardware (not shown) via 11 Gb/s XFI connectors. A significant advantageof the configuration in FIG. 3C is that the 2×1 combiner and 1×2 AWGwavelength separator are both moved out of the CFP module 320, thereforefurther reducing the cost and saving the space and power consumption ofthe CFP module.

As shown in FIG. 3C, the 1×2 AWG device 314 is now located between aconventional 40-ch or 80-ch DWDM MUX/DEMUX box 310 and a transmissionlink. In essence, this embodiment utilizes the cyclic nature of 1×2 AWGsor a free-space de-interleaver to separate the two optical carriers (25GHz spaced) in every 50 GHz ITU window.

The same principle in FIG. 3A-3C can be applied to the case of a 56 Gb/sCFP module as shown in FIGS. 4A and 4B. In particular, FIG. 4A shows anexemplary hardware and optical configuration of a 56 Gb/s CFP MSAtransceiver module 400. As illustrated, on a host board 420 are mountedan external 5 of 10 Gb/s FEC chips 421, electrically connected viastandard XFI interface to a gear box 422, this gear box is only half ofwhich is used in a standard 100 Gb/s gear box (and hence “½”), whichconverts 10× 10 Gb/s lines to 4×25 Gb/s lines. Within the module 420,multiplexing and demultiplexing between 5×11 Gb/s and 2×28 Gb/s areperformed, similar to the functions performed by MUX/DEMUX 124, 134 asin the embodiment of FIG. 3A. In the example of FIG. 4A, duobinaryencoders can be included in the gear box 422, or they can be stand-alonechips immediately after the gear box.

The gear box 422 separates the 56 Gb/s signal into two ˜28 Gb/s signals,each separately passing through drivers 126 a, 126 b, then through lowpass filters (LPFs) 125 a, 125 b. The order of the amplifier and the LPFcan be reversed. The signals can be amplified in this embodiment bydrivers 126 a, 126 b with a small enough group delay that a 20-28 Gb/ssignal will not be distorted, though in some embodiments these driversmay not be required. The low-pass filtered and amplified signals thendrive respective tunable 10G TX 127 a, 127 b. Optical signals fromrespective tunable 10G TX 127 a, 127 b, which are small enough to fitinto the CFP MSA module 420, are passed through a 2×1 optical coupler orPMBC 129 to the transmission line.

FIG. 4B shows a variation of FIG. 4A. On the transmitter side, there isno 2×1 combiner 129 to combine the two optical wavelengths, and thewavelengths are combined at a 2×1 interleaver 310 outside the CFPmodule. The operation principle is the same as FIG. 3C.

On the receiver side of FIG. 4B, there is no 1×2 AWG slicer 130, as inFIG. 4A, and the wavelength separation is done in an 1×2 de-interleaver315 within the DWDM transmission infrastructure. After the 1×2de-interleaver 315, each received optical signal is separated and inputto the DEMUX 316 a and 316 b of the external DWDM box 310, respectively.An output fiber from the odd-channel DEMUX 316 a is connected to a first20 Gb/s receiver 427 a, and an output fiber from the even-channel DEMUX316 b is connected to a second 20 Gb/s receiver 427 b. Electronicdispersion compensators (EDCs) 132 a, 132 b are connected to the 20 Gb/sreceivers 427 a and 427 b, respectively. Thereafter, the receivedsignals are input into the ½ gear box 422, and the resultingdemultiplexed signal is then transmitted (via e.g., XFI interface) tothe external FEC device (not shown).

A difference between the configurations in FIGS. 3A, 3B, 3C and FIGS.4A, 4B lies in the first interface chip. In FIGS. 4A and 4B, the firstinterface chip is now a gear box 422 commonly used to convert 10×10G to4×25G. As used in the exemplary embodiment of FIGS. 4A and 4B, only halfof the gear box is used, thus in effect converting 5×11.3 Gb/selectrical signals to 2×28 Gb/s electrical signals. Due to the fact thatthe gear box 422 does not have FEC functions in this exemplaryembodiment (though this would be an alternative implementation), thoseFEC functions could be sitting on a host board 420.

It is interesting to note that in FIGS. 3A, 3B and 3C, and FIGS. 4A and4B, each CFP transceiver provides a 56 Gb/s capacity within 50 GHz, andthus 112 Gb/s within 100 GHz can be obtained if two such CFP modules areused. This approach can provide probably the lowest cost of 100 Gb/scapacity in 100 GHz via two hot pluggable CFP modules, as opposed totechniques such as coherent detection, which is structurally morecomplex, is not as small, consumes more electrical power, and is nothot-pluggable.

FIG. 5 shows the configuration of a client-side 100 Gb/s CFP opticaltransceiver. It is composed of four T-TOSAs (or fixed wavelength TOSAs)526 a, 526 b, 526 c, 526 d and four ROSAs (receiver optical subassemblies) 527 a, 527 b, 527 c, 527 d. Externally modulated InP MZI areused considering the space constraint if CFP MSA modules are to be usedin this exemplary embodiment. Essentially, this embodiment can have fourXFP or T-XFP opto-electronic transmitter components placed inside a CFPmodule 500. Most importantly, this configuration also allows both4-wavelength MUX and DEMUX be integrated in the same module, whichimplies that wavelength spacing is at least 100 GHz-spaced so that the4-wavelength mux/demux is small enough to be accommodated. In this case,a 100 Gb/s transmission requires a bandwidth of 100 GHz×=400 GHz, whichis currently very good for client-side applications. Of course, a FEC521 could be added if the embodiment of FIG. 5 is used on a line-sideapplication.

In detail, FIG. 5 shows an exemplary hardware and optical configurationof a 100 Gb/s CFP MSA transceiver module 500. As illustrated, on a hostboard 520 are mounted an external 10×10 Gb/s FEC chip(s) 521 (note thatthe dashed box implies that this FEC box is normally not required for aclient-side CFP application), electrically connected via standard XFIinterface to a conventional gear box 522. In the example of FIG. 5, thegear box 522 includes duobinary encoders, but it is possible that thisfunction be incorporated in 4 independent chips at the 4 outputs of thegear box.

The gear box 522 separates the 100 Gb/s signal into four ˜25 Gb/ssignals, each encoded with a differential encoder (or duobinaryprecoder), each separately passing through drivers 524 a, 524 b, 524 c,524 d, then through low pass filters (LPFs) 523 a, 523 b, 523 c, 523 d(which can be separate filters or different ports of the same LPF). Thedifferential encoder can be included in the gear box, or can be locatedright at the output port of the gear box as a separate chip. Thefiltered signals can be amplified in this embodiment by drivers 524 a,524 b, 524 c, 524 d, that have a flat group delay such that 20-28 Gb/ssignals will not be distorted, though in some embodiments these driversmay not be required. The low-pass filtered and amplified signals thendrive tunable 10G TOSA's 526 a, 526 b, 526 c and 526 d.

The modulated optical outputs from the tunable 10G TOSA's 526 a, 526 b,525 c, 525 d are then input to a 4×1 DWDM coupler 529 a for transmissionon a transmission line of for instance a local area network (LAN) DWDMsystem. Note that the channel spacing between wavelengths in the LANapplication does not have to be as dense as 19-25 GHz, rather, it can beas wide as several nanometers.

On the receive side, each received optical signal is separated by a 1×4DWDM 529 b, and the respective signals are fed to respective 25 Gb/sROSAs 526 a, 526 b, 526 c, 526 d, and then onto an optional electronicdispersion compensators (EDC) 528 a, 528 b, 528 c, 528 d. Thereafter,the received signals are input into the gear box 522, and the resultingdemultiplexed signals are then transmitted (via, e.g., XFI interface) tothe host board. In a LAN application, normally the host board does nothave an FEC device. However, if there is a need for longer distancetransmission, an optional FEC can be also added. In that case, due tothe FEC overhead, the data rate per lane will be increased from 25 Gb/sto ˜28 Gb/s.

While the foregoing disclosure discusses illustrative aspects and/orembodiments, it should be noted that various changes and modificationscould be made herein without departing from the scope of the describedaspects and/or embodiments as defined by the appended claims.Furthermore, although elements of the described aspects and/orembodiments may be described or claimed in the singular, the plural iscontemplated unless limitation to the singular is explicitly stated.Additionally, all or a portion of any aspect and/or embodiment may beutilized with all or a portion of any other aspect and/or embodiment,unless stated otherwise.

1. An N-carrier optical wavelength division modulator (WDM)transponder/transceiver, comprising: at least one pair of 10 Gb/soptical transmitters whose wavelengths are within a 50 or 100 GHz ITU-Twindow; and an opto-electronic control circuit driving each opticaltransmitter, wherein said opto-electronic control circuit includes amultiplexer outputting a control signal, wherein each opticaltransmitter is driven by the electrical control signal output by theopto-electronic control circuit according to a band-limited optical duobinary modulation technique at 20˜28 Gb/s.
 2. An N-carrier opticalwavelength division modulator (WDM) transponder/transceiver inaccordance with claim 1, wherein said opto-electronic control currentfurther comprises: at least one electronic device to convert a signalfrom an interface to N lanes of 20˜28 Gb/s differentially-encoded NRZsignals; N driver amplifiers to amplify the N lanes of 20˜28 Gb/s NRZsignals, respectively, wherein the group delay variation of eachamplifier is low enough so as not to distort the 20˜28 Gb/s NRZ signals;and N electronic low-pass filters receiving the amplified signals andserving as duobinary encoders; and wherein said at least one pair of 10Gb/s optical transmitter further comprise: N 10 Gb/s opticaltransmitters converting the encoded signals into optical signals havingN different wavelengths; and an optical combiner to combine the twowavelengths generated from the N 10 Gb/s optical transmitters, andwherein said electronic device has sufficient electronic buffer tomanage a the skew between the 20˜28 Gb/s lanes.
 3. An N-carrier opticalwavelength division modulator (WDM) transponder/transceiver inaccordance with claim 2, wherein the 10 Gb/s optical transmitterscontains a standard or miniaturized integrated tunable laser assembly(ITLA).
 4. An N-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 2, wherein the 10 Gb/soptical transmitters contains a tunable or fixed-wavelength transmitteroptical subassembly (TOSA).
 5. An N-carrier optical wavelength divisionmodulator (WDM) transponder/transceiver in accordance with claim 2,wherein each tunable 10 Gb/s optical transmitter contains a zero-chirpor pre-chirped lithium-niobate, or InP, or polymer-based opticalmodulator.
 6. An N-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 2, wherein the opticalcombiner is a polarization maintaining beam combiner.
 7. An N-carrieroptical wavelength division modulator (WDM) transponder/transceiver inaccordance with claim 2, wherein the optical combiner is an opticalcoupler.
 8. An N-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 2, further comprisingat least one pair of 20˜28 Gb/s optical receivers, wherein each 20˜28Gb/s receiver contains at least one 20˜28 Gb/s electronic dispersioncompensator (EDC).
 9. An N-carrier optical wavelength division modulator(WDM) transponder/transceiver in accordance with claim 2, wherein the atleast one electronic output device that converts N lanes of 20˜28 Gb/sNRZ signals to SFI5.1 interface contains N 20˜23 Gb/s EDCs.
 10. AN-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 1, wherein the entiretransponder/transceiver is contained within one of a 300-pin MSA packageor a CFP MSA package.
 11. A two-carrier optical wavelength divisionmodulator (WDM) transponder/transceiver, comprising: at least oneelectronic input device to convert a signal from an SFI5.1 interface totwo lanes of 20˜28 Gb/s differentially-encoded NRZ signals; one pair ofdriver amplifiers to amplify the two lanes of 20˜28 Gb/s NRZ signals,respectively, wherein the group delay variation of each amplifier is lowenough so as not to distort the 20˜28 Gb/s NRZ signals; one pair ofelectronic low-pass filters receiving the amplified signals and servingas duobinary encoders; one pair of tunable 10 Gb/s optical transmittersconverting the encoded signals into optical signals having two differentwavelengths; an optical combiner to combine the two wavelengthsgenerated from the two tunable 10 Gb/s optical transmitters; an opticalwavelength slicer to separate the two wavelengths received from thetransmission line; one pair of 20-23 Gb/s optical receivers; and atleast one electronic output device to convert two lanes of 20˜28 Gb/sNRZ signals to an SFI5.1 interface.
 12. A two-carrier optical wavelengthdivision modulator (WDM) transponder/transceiver in accordance withclaim 11, wherein the electronic device has sufficient electronic bufferto manage skew between the two 20˜28 Gb/s lanes. 13-18. (canceled)
 19. Atwo-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 11, wherein thewavelength slicer is a 1 input×2 output cyclic array-waveguide with acycle of 50 or 100 GHz. 20-23. (canceled)
 24. A two-carrier opticalwavelength division modulator (WDM) transponder/transceiver, comprising:at least one electronic input device to convert 4× 10 Gb/s XFI interfaceto two lanes of 20˜28 Gb/s differentially-encoded NRZ signals; one pairof driver amplifiers to amplify the two lanes of 20˜28 Gb/s NRZ signals,respectively, wherein the group delay variation of each amplifier is lowenough so as not to distort the 20˜28 Gb/s NRZ signals; one pair ofelectronic low-pass filters receiving the amplified signals and servingas duobinary encoders; one pair of tunable 10 Gb/s optical transmittersconverting the encoded signals into optical signals having two differentwavelengths; an optical combiner to combine the two wavelengthsgenerated from the two tunable 10 Gb/s optical transmitters; an opticalwavelength slicer to separate the two wavelengths received from thetransmission line; one pair of 20˜28 Gb/s optical receivers; and atleast one electronic output device to convert two lanes of 20˜28 Gb/sNRZ signals to an SFI5.1 interface.
 25. A two-carrier optical wavelengthdivision modulator (WDM) transponder/transceiver in accordance withclaim 24, wherein the electronic device has sufficient electronic bufferto manage skew between the two 20˜28 Gb/s lanes. 26-30. (canceled)
 31. Atwo-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 24, wherein the channelspacing between the two optical wavelengths of the two tunable 10 Gb/soptical transmitters is between 19 and 25 GHz. 32-36. (Cancelled)
 37. Atwo-carrier optical wavelength division modulator (WDM)transponder/transceiver, comprising: at least one electronic inputdevice to convert 5× 10 Gb/s XFI interface to two 2 lanes of 27˜28 Gb/sdifferentially-encoded NRZ signals; one pair of driver amplifiers toamplify the two lanes of 27˜28 Gb/s NRZ signals, respectively, whereinthe group delay variation of each amplifier is low enough so as not todistort the 27˜28 Gb/s NRZ signals; one pair of electronic low-passfilters receiving the amplified signals and serving as duobinaryencoders; one pair of tunable 10 Gb/s optical transmitters convertingthe encoded signals into optical signals having two differentwavelengths; an optical combiner to combine the two wavelengthsgenerated from the two tunable 10 Gb/s optical transmitters; an opticalwavelength slicer to separate the two wavelengths received from thetransmission line; one pair of 27˜28 Gb/s optical receivers; and atleast one electronic output device to convert two lanes of 27˜28 Gb/sNRZ signals to a 5× 10 Gb/s XFI interface.
 38. A two-carrier opticalwavelength division modulator (WDM) transponder/transceiver inaccordance with claim 37, wherein the electronic device has sufficientelectronic buffer to manage the skew between two 20˜28 Gb/s lanes.39-41. (canceled)
 42. A two-carrier optical wavelength divisionmodulator (WDM) transponder/transceiver in accordance with claim 37,wherein the optical combiner is a polarization maintaining beamcombiner. 43-49. (canceled)
 50. A four-carrier optical wavelengthdivision modulator (WDM) transponder/transceiver, comprising: at leastone electronic input device to convert 5× XFI interface to four lanes of25 Gb/s differentially-encoded NRZ signals; four driver amplifiers toamplify the four lanes of 25 Gb/s NRZ signals, respectively, wherein thegroup delay variation of each amplifier is low enough so as not todistort the 25 Gb/s NRZ signals; four electronic low-pass filtersreceiving the amplified signals and serving as duobinary encoders; four10 Gb/s optical transmitters converting the encoded signals into opticalsignals having four different wavelengths; an optical combiner tocombine the four wavelengths generated from the four 10Gb/s opticaltransmitters; an optical wavelength slicer to separate the fourwavelengths received from the transmission line; four 25 Gb/s opticalreceivers; and at least one electronic output device to convert fourlanes of 25 Gb/s NRZ signals to an 10× XFI interface.
 51. A four-carrieroptical wavelength division modulator (WDM) transponder/transceiver inaccordance with claim 50, wherein the electronic device has sufficientelectronic buffer to manage skew among the four 25 Gb/s lanes. 52-56.(canceled)
 57. A four-carrier optical wavelength division modulator(WDM) transponder/transceiver in accordance with claim 50, wherein thechannel spacing between the any two neighbor optical wavelengths of fourtransmitters is up to a few nanometers.
 58. A four-carrier opticalwavelength division modulator (WDM) transponder/transceiver inaccordance with claim 50, wherein said optical slicer is a 1 input×4output cyclic array-waveguide with a cycle of 50 or 100 GHz. 59-62.(canceled)
 63. An N-carrier optical wavelength division modulator (WDM)transponder/transceiver, comprising: at least one electronic device toconvert SFI5.1 interface to N lanes of 10 or 20˜23 Gb/sdifferentially-encoded NRZ signals; N driver amplifiers to amplify the Nlanes of 10 or 20˜23 Gb/s NRZ signals, respectively, wherein the groupdelay variation of each amplifier is low enough so as not to distort the10 or 20˜23 Gb/s NRZ signals; N electronic low-pass filters receivingthe amplified signals and serving as duobinary encoders; N 10 or 20˜23Gb/s optical transmitters converting the encoded signals into opticalsignals having N different wavelengths, wherein all N differentwavelengths are within one of a 50 GHz window or a 100 GHz window; N 10or 20˜23 Gb/s optical receivers; and at least one electronic device toconvert N lanes of 10 or 20˜23 Gb/s NRZ signals back to an SFI5.1interface, wherein N is an positive integer.
 64. An N-carrier opticalwavelength division modulator (WDM) transponder/transceiver inaccordance with claim 63, wherein the electronic device has sufficientelectronic buffer to manage the skew between the N 10 or 20˜23 Gb/slanes. 65-67. (canceled)
 68. An N-carrier optical wavelength divisionmodulator (WDM) transponder/transceiver in accordance with claim 63,wherein the channel spacing between the N optical wavelengths of the Ntransmitters is approximately one of 12.5 GHz or 25 GHz. 69-73.(canceled)
 74. A two-carrier optical wavelength division modulator (WDM)transponder/transceiver, comprising: at least one electronic inputdevice to convert 4× XFI interface to two lanes of 20˜23 Gb/sdifferentially-encoded NRZ signals; one pair of driver amplifiers toamplify the two lanes of 20˜23 Gb/s NRZ signals, respectively, whereinthe group delay variation of each amplifier is low enough so as not todistort the 20˜23 Gb/s NRZ signals; one pair of electronic low-passfilters receiving the amplified signals and serving as duobinaryencoders; one pair of tunable 10 Gb/s optical transmitters convertingthe encoded signals into optical signals having two differentwavelengths; one pair of 20˜23 Gb/s optical receivers; and at least oneelectronic output device to convert two lanes of 20˜23 Gb/s NRZ signalsback to 4× XFI interface.
 75. A two-carrier optical wavelength divisionmodulator (WDM) transponder/transceiver in accordance with claim 74,wherein the electronic device has sufficient electronic buffer to managethe skew between the two 20˜23 Gb/s lanes. 76-78. (canceled)
 79. Atwo-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 74, wherein the channelspacing between the two optical wavelengths of the two transmitters is25 GHz. 80-84. (canceled)
 85. A two-carrier optical wavelength divisionmodulator (WDM) transponder/transceiver, comprising: at least oneelectronic input device to convert 5× XFI interface to two lanes of27˜28 Gb/s differentially-encoded NRZ signals; one pair of driveramplifiers to amplify the two lanes of 27˜28 Gb/s NRZ signals,respectively; the group delay variation of each amplifier is low enoughso as not to distort the 27˜28 Gb/s NRZ signals; one pair of electroniclow-pass filters receiving the amplified signals and serving asduobinary encoders; one pair of tunable 10 Gb/s optical transmittersconverting the encoded signals into optical signals having two differentwavelengths; one pair of 27˜28 Gb/s optical receivers; and at least oneelectronic output device to convert two lanes of 27˜28 Gb/s NRZ signalsback to an 5× XFI interface.
 86. A two-carrier optical wavelengthdivision modulator (WDM) transponder/transceiver in accordance withclaim 85, wherein the electronic device has sufficient electronic bufferto manage the skew between the two 27-28 Gb/s lanes. 87-89. (canceled)90. A two-carrier optical wavelength division modulator (WDM)transponder/transceiver in accordance with claim 85, wherein the channelspacing between the two optical wavelengths of the two transmitters is25 GHz. 91-95. (canceled)